Malaria ever has been, and is yet, the great barrier against the invasion of the tropics by the white races; nor has its injurious influence been confined to the deaths that it causes, for these gaps in the fighting line might be filled by fresh levies drawn from the wholesome North. Its fearfully depressing and degenerating effects upon even those who recover from its attacks have been still more injurious. It has been held by careful students of tropical disease and conditions that no small part of that singular apathy and indifference which steal over the mind and body of the white colonist in the tropics, numbing even his moral sense, and alternating with furious outbursts of what the French have termed "tropical wrath," characterized by unnatural cruelty and abnormal disregard for the rights of others, is the deadly work of malaria. It is the most powerful cause, not merely of the extinction of the white colonist in the tropics, but of the peculiar degeneracy--physical, mental, and moral--which is apt to steal over even the survivors who succeed in retaining a foothold. Two particularly ingenious investigators have even advanced the theory that the importation of malaria into the islands of Greece and the Italian peninsula by soldiers returning from African and Southern Asiatic conquests had much to do with accelerating, if not actually promoting, the classic decay of both of these superb civilizations. To come nearer home, there can be little question that the baneful, persistent influence of malaria, together with the hookworm disease, has had much to do both with the degeneracy of the Southern "cracker," or "mean white," and with those wild outbursts of primitive ferocity in all classes which take the form of White Cap raids and lynching mobs.